Solar thermal absorber element

ABSTRACT

A solar thermal collector includes a solar thermal absorber element which includes a cover glass, a direct-flow absorber, a fore thermoplastic sealing for attaching the cover glass and absorber to each other leaving a distance (h 1 ) therebetween, and a fore sealed space, formed by the cover glass, absorber, and fore sealing. The fore space is filled up with a first low thermal conductive gas. The element further includes a back insulation part, a back thermoplastic sealing for attaching the insulation part and the absorber to each other leaving a distance (h 2 ) therebetween, and a back sealed space, formed by the insulation part, absorber, and back sealing. The back space is filled up with a second low thermal conductive gas. The element may include a TPS-direct-flow absorber-glass element, wherein the back glass insulation part is hermetically sealed with the TPS sealing and the back space is filled with the second gas.

TECHNICAL FIELD

The application relates generally to a solar thermal absorber element.

BACKGROUND OF THE INVENTION

Sand, salt, and insects, which have invaded inside a structure of solarthermal collectors along flowing air, cause damages decreasing alifetime and an efficiency of the collectors.

In order to eliminate these damages, it has been developed athermoplastic spacer (TPS) sealed absorber module, wherein a cover glassis sealed with an absorber by a TPS.

The TPS sealed module protects the absorber by preventing undesirablesand, salt, and insects to invade inside the absorber element.

However, manufacturing costs of collectors, even if absorber moduleswould be TPS sealed modules, have been high, because manufacturing stepsin series production comprise lots of manual work when an insulation isadded and modules are mounted manually into a collector frame.

SUMMARY

One object of the invention is to withdraw the above-mentioned drawbackand provide a solar thermal absorber element, which comprises a TPSsealed back insulation that enables to manufacture elements in massproduction by existing automatic production lines that are used formanufacturing of a TPS insulation glass.

One object of the invention is fulfilled by providing a solar thermalabsorber element of claim 1, a solar thermal collector of claim 6, and amethod of claim 7.

One embodiment of the invention is a solar thermal absorber element thatcomprises a cover glass, a direct-flow absorber, a fore thermoplasticsealing for attaching the cover glass and the absorber to each other sothat there is a distance therebetween, and a fore sealed space, which isformed by the cover glass, the absorber, and the fore sealing. The forespace is filled up with a first low thermal conductive gas. The elementfurther comprises a back insulation part, a back thermoplastic sealingfor attaching the insulation part and the absorber to each other so thatthere is a distance therebetween, and a back sealed space, which isformed by the insulation part, the absorber, and the back sealing. Theback space is filled up with a second low thermal conductive gas.

The direct-flow absorber refers to an absorber, wherein heat transportfluid, e.g. water, air, or antifreeze, circulates inside a structure ofthe absorber.

The thermoplastic sealing refers to a sealing (spacer), which is made bya thermoplastic spacer (TPS) technology.

The low thermal conductive gas refers to a gas, which has a low thermalconductivity, e.g. noble gases. The noble gas can be e.g. argon,krypton, or xenon.

The roll-bond absorber refers to an absorber, which comprises at leastone tube and which is provided by a roll-bond technology.

The highly selective vacuum coating refers to e.g. a coating, which isdeposited in vacuum and which forms a selective absorber coating with asolar absorbance more than 96% with low thermal emission by radiation inthe infrared.

One embodiment of the invention is a solar thermal collector thatcomprises an absorber element. The element comprises a cover glass, adirect-flow absorber, a fore thermoplastic sealing for attaching thecover glass and the absorber to each other so that there is a distancetherebetween, and a fore sealed space, which is formed by the coverglass, the absorber, and the fore sealing. The fore space is filled upwith a first low thermal conductive gas. The element further comprises aback insulation part, a back thermoplastic sealing for attaching theinsulation part and the absorber to each other so that there is adistance therebetween, and a back sealed space, which is formed by theinsulation part, the absorber, and the back sealing. The back space isfilled up with a second low thermal conductive gas.

One embodiment of the invention is a method for manufacturing a solarthermal absorber element. The element comprises a cover glass, adirect-flow absorber, a fore and back thermoplastic sealings, a foresealed space, and a back insulation part. The method comprisesattaching, by the fore sealing, the cover glass and the absorber to eachother so that there is a distance therebetween, whereupon the coverglass, the absorber, and the fore sealing form the fore space, fillingup the fore space with a first low thermal conductive gas. The methodfurther comprises attaching, by the back sealing, the insulation partand the absorber to each other so that there is a distance therebetween,whereupon the insulation part, the absorber, and the back sealing formthe back space, and filling up the back space with a second low thermalconductive gas.

Further embodiments of the invention are defined in dependent claims.

The features recited in depending claims are mutually freely combinableunless otherwise explicitly stated.

The below definitions of verbs and terms shall be applied, unless adifferent definition is given in the claims or elsewhere in thisdescription.

The verb “to comprise” is used in this document as an open limitationthat neither excludes nor requires the existence of also unrecitedfeatures. The verbs “to include” and “to have/has” are defined as tocomprise.

The terms “a”, “an”, and “at least one”, as used herein, are defined asone or more than one and the term “plurality” is defined as two or morethan two.

The term “another”, as used herein, is defined as at least a second ormore.

The term “or” is generally employed in its sense comprising “and/or”unless the content clearly dictates otherwise.

BRIEF DESCRIPTION OF THE FIGURES

The embodiments of the invention will be described with reference to theaccompanying figures, in which

FIG. 1a represents a cross-section of a solar thermal absorber elementand

FIG. 1b represents a cross-section of a solar thermal collector.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1a represents a cross-section of solar thermal absorber element(module) 100.

The element 100 comprises a cover glass 110 and a direct-flow absorber120.

The glass 110 covers the absorber 120 for mechanical damages, insects,and dust.

The glass 110 may be e.g. a highly transparent antireflective safetyglass that allows solar radiation to pass to the absorber 120 andreduces heat losses from the absorber 120.

The absorber 120 is configured to absorb the solar radiation.

The absorber 120 comprises at least one heat transport tube 126 thatforms a continuous heat transport channel, which has an inlet 127 a andan outlet 127 b. The channel is configured to circulate a heat transportfluid, e.g. water, air, or anti-freeze, inside the absorber 120.

The inlet 127 a and the outlet 127 b are possible to connect to externaldevices, e.g. a tubing of a solar thermal collector 190 or its adaptermeans.

The absorber 120, which has a rigid structure, keeps a first distance h₁between the glass 110 and the absorber 120 constant—i.e. prevents theabsorber 120 to bend towards the glass 110—in order to minimize thermallosses. The thermal losses are minimized when the distance h₁ is 10 mm.If the absorber 120 bends towards the glass 110 so that the distance h₁is less than 10 mm, the thermal losses increase dramatically.

The absorber 120 may be a roll-bond absorber that is formed from e.g.two aluminium plates by a roll-bond technology.

A pattern and size of the tube(s) 126 are printed on an inner surface ofone plate by a special silk screen and ink. The plates are bondedtogether by a rolling process, whereupon the printed pattern remainsbetween inner surfaces of the bonded plates. The tube(s) 126 is formedbetween the plates by inflating compressed air through the printedpattern.

Alternatively, the absorber 120 may be a direct-flow absorber that isformed from e.g. two steel, stainless steel, or copper plates.

The tube(s) 126 is formed similarly as in the roll-bond absorber 120except the bonding that is provided by welding the plates together.

A design of tube(s) 126 may be e.g. a single twisting tube 126 and/or amulti-branched tube 126, which is configured to decrease a flowresistant of the heat transport fluid.

In addition, the absorber 120 may comprise a coating 150, which isconfigured to absorb light.

The coating 150 may be on a fore surface 122 of the absorber 120,wherein it faces the glass 110.

The coating 150 may be deposited in vacuum on the entire and completeabsorber 120 at once by a physical vapour deposition (PVD) processand/or a plasma-enhanced chemical vapour deposition (PECVD) process.

The coating 150 may be a highly selective vacuum multilayer coating thatcomprises e.g. three deposited layers 152, 154, 156.

A first layer 152 on the fore surface 122 is configured to absorb lightand to prevent a diffusion of elements from an absorber material thatdecreases a performance of the absorber 120.

A composition of the layer 152 may comprise titanium, aluminium,nitrogen, and one of following elements: silicon, yttrium, cerium, andchromium.

The composition may be e.g. (Ti_(x)Al_(y)Si_(z))N_(a). Alternatively, atleast one of Y, Ce, and Cr may be used additionally or instead of Si.

Indices x, y, z, a, and b, indicate a stoichiometric ornon-stoichiometric composition of the layers 152, 154, 156.

Values of the layer 152 for x, y, z, and a may be e.g. 0.4; 0.5; 0.1;and 1.0 respectively. Typically, the values are 0.3-0.5; 0.3-0.6;0.03-0.2; and 0.9-1.1 respectively.

The layer 152 may have a layer thickness between e.g. 10-600 nm.

A second intermediate layer 154 on the layer 152 is configured to absorblight and to increase an interference at selected wavelengths.

A composition of the layer 154 may comprise Ti, Al, N, oxygen, and oneof following elements: Si, Y, Ce, and Cr.

The composition may be e.g. (Ti_(x)Al_(y)Si_(z))N_(a)O_(b).Alternatively, at least one of Y, Ce, and Cr may be used additionally orinstead of Si.

Values of the layer 154 for x, y, z, a, and b may be e.g. 0.4; 0.5; 0.1;0.8; and 0.3 respectively. Typically, the values are 0.3-0.5; 0.3-0.6;0.03-0.2; 0.2-0.8; and 0.2-0.8 respectively.

The layer 154 may have a layer thickness between e.g. 10-150 nm.

A third top layer 156 on the layer 154 is configured to serve as anantireflection layer and to isolate the coating 150 from a surroundinggas 136.

A composition of the layer 156 may comprise Ti, Al, Si, N, and O.

The composition may be e.g. (Ti_(x)Al_(y)Si_(z))N_(a)O_(b).

Typically, values of the layer 156 for x, y, z, a, and b may be e.g.0-0.2; 0-0.2; 0-1; 0-2; and 0-2 respectively.

The layer 156 may have a layer thickness between e.g. 50-250 nm.

The coating 150 may be a selective absorber coating, e.g. a so-calledMEMO multilayer coating, wherein the layer 152 is a TiAlSiN layer, thelayer 154 is a TiAl—SiON layer, and the layer 156 is a SiO₂ layer.

In addition, the element 100 comprises a fore thermoplastic spacer (TPS)sealing 130 that attaches the glass 110 and the absorber 120 to eachother so that there is a certain distance h₁, e.g. 10, 15, or 20 mm,between the glass 110 and the absorber 120.

The attachment is made by a TPS technology in an automatic productionline. The sealing 130 is injected on the glass 110 for achieving adesired sealing thickness and the distance h₁. The glass 110 with thesealing 130 and the absorber 120 are pressed together so that a foresealed space 134 is formed by the glass 110, the absorber 120, and thesealing 130 that surround the space 134.

The sealing 130 is a gas tight sealing that seals the space 134hermetically.

The sealing 130 may be a high temperature sealing material, e.g. a butylsealing.

While the glass 110 and the absorber 120 are pressed together, a lowthermal conductive gas 136, e.g. an argon gas, is injected into thespace 134 so that it is filled up with the gas 136.

The glass 110, the absorber 120, and the sealing 130 keep the gas 136 inthe space 134 and prevent the gas 136 to flow outside the element 100.

The gas 136 reduces thermal losses by convection.

In addition, the element 100 comprises a fore secondary sealing 140,which is attached to the sealing 130, and between the glass 110 and theabsorber 120.

The sealing 140 protects the sealing 130 and carries a weight of theabsorber 120.

The sealing 140 may be e.g. a silicon sealing.

In addition, the element 100 comprises a back insulation part 160 thatcovers the absorber 120 for mechanical damages and supports a heatinsulation of the element 100 by reducing heat losses from the absorber120.

In addition, the insulation part 160 covers the absorber 120 formechanical damages, insects, and dust.

The insulation part 160 may be e.g. a glass, a polyurethane (PUR) board,or a polyisocyanurate (PIR) board, whereupon it is a corrosion free.

In addition, the element 100 comprises a back TPS sealing 170 thatattaches the insulation part 160 and the absorber 120 to each other sothat there is a second distance h₂, e.g. 10, 15, or 20 mm, therebetween.

The attachment is made correspondingly in the automatic production lineas the attachment of the glass 110 and the absorber 120 so that a backsealed space 174 is formed by the insulation part 160, the absorber 120,and the sealing 170 that surround the space 174.

The attachments of the glass 110 and the insulation part 160 may be madeat the same time or successive production steps.

The sealing 170 is a gas tight sealing that seals the space 174hermetically and it may be e.g. a butyl sealing.

The space 174 is filled up with a second low thermal conductive gas 176,e.g. an argon gas, correspondingly as the space 134.

The additions of the gases 136, 176 may be made at the same time orsuccessive production steps in accordance with the TPS technology.

The insulation part 160, the absorber 120, and the sealing 170 keep thegas 176 in the space 174 and prevent the gas 136 to flow outside theelement 100.

The gas 176 reduces thermal losses by convection.

In addition, the element 100 comprises a back secondary sealing 180,which is attached to the sealing 170, and between the insulation part160 and the absorber 120.

The sealing 180, which may be e.g. a silicon sealing, protects thesealing 170 and carries a weight of the absorber.

The formations of the sealings 140, 180 may be made at the same time orsuccessive production steps in accordance with the TPS technology.

The hermetically sealed space 134 preserves an efficiency of theabsorber 120, when it prevents dust or insects to let in it, whereuponthere is no efficiency change during a lifetime of the absorber 120because of the dust or insects.

In addition, the hermetically sealed space 134 prevents a watercondensation on the glass 110, whereupon the element 100 can start toproduce energy earlier on a morning.

FIG. 1b represents a cross-section of a solar thermal collector 190 thatcomprises the element 100 represented in FIG. 1 a.

The collector 190 is a flat-plate collector for e.g. high temperaturesthat may be used e.g. in solar cooling applications.

In addition, the collector 190 may comprise a collector frame 192 thatcover the collector 190 for mechanical damages, insects, and dust.

The frame 192 may be made of e.g. an aluminium, composite plastic, orwood.

The frame 192 comprising at least one support (insulation) element 194on its inner surface.

The support element(s) 194 supports the element 100, when the element100 is mounted into the frame 190.

In addition, the support element(s) 194 thermally insulates the element100 and minimize environmental effects.

The support element(s) 194 may be e.g. mineral or wood fiber wool.

The element 100 is attached to the frame 192 by gluing edges of theglass 110 and the insulation part 160 with a high temperature and UVresistant glue 190, which prevents water to penetrate inside thecollector 190, and spacer tapes.

The element 100 enables to use cheaper materials for the supportelement(s) 194, because there is no condensation of any evaporatedcomponents from the support element(s) 194.

Alternatively, the collector 190 may be without the frame 192 and thesupport element(s) 194, whereupon its cross-section is in accordancewith FIG. 1 a.

In addition, the collector 190 may comprise adapter means and tubingmeans so that the the tube(s) 126 of the element 100 is possible toconnect to the collector 190 by the inlet 127 a, the outlet 127 b, theadapter means, and the tubing means.

In addition, the element 100 enables to build very effective modularlarge area collectors for process and district heating systems byconnecting several collectors 190.

The invention has been now explained above with reference to theaforesaid embodiments and the several advantages of the invention havebeen demonstrated.

It is clear that the invention is not only restricted to theseembodiments, but comprises all possible embodiments within the scope ofthe invention thought and the following claims.

1. A solar thermal absorber element (100) comprising a cover glass(110), a direct-flow absorber (120), a fore thermoplastic sealing (130)for attaching the cover glass and the absorber to each other so thatthere is a distance (h₁) therebetween, and a fore sealed space (134),which is formed by the cover glass, the absorber, and the fore sealing,and which is filled up with a first low thermal conductive gas (136),wherein the element further comprises a back insulation part (160), aback thermoplastic sealing (170) for attaching the insulation part andthe absorber to each other so that there is a distance (h₂)therebetween, and a back sealed space (174), which is formed by theinsulation part, the absorber, and the back sealing, and which is filledup with a second low thermal conductive gas (176).
 2. The element ofclaim 1, which further comprises a back secondary sealing (180), whichis attached to the back sealing and between the insulation part and theabsorber, the back secondary sealing is configured to protect the backsealing and to carry a weight of the absorber.
 3. The element of claim1, wherein the insulation part is a glass, a polyurethane board, or apolyisocyanurate board.
 4. The element of claim 1, wherein the absorberis a roll-bond absorber (120) that comprises a highly selective vacuumcoating (150) on its fore surface (122), the coating is configured toabsorb light.
 5. The element of claim 1, wherein the second low thermalconductive gas is an argon gas.
 6. A solar thermal collector (190)comprising an absorber element (100) of claim 1, which comprises a coverglass (110), a direct-flow absorber (120), a fore thermoplastic sealing(130) for attaching the cover glass and the absorber to each other sothat there is a distance (h₁) therebetween, a fore sealed space (134),which is formed by the cover glass, the absorber, and the fore sealing,and which is filled up with a first low thermal conductive gas (136), aback insulation part (160), a back thermoplastic sealing (170) forattaching the insulation part and the absorber to each other so thatthere is a distance (h₂) therebetween, and a back sealed space (174),which is formed by the insulation part, the absorber, and the backsealing, and which is filled up with a second low thermal conductive gas(176).
 7. A method for manufacturing a solar thermal absorber element(100) of claim 1, which element comprises a cover glass (110), adirect-flow absorber (120), a fore and back thermoplastic sealings (130,170), a fore sealed space (134), and a back insulation part (160), themethod comprises attaching, by the fore sealing (130), the cover glassand the absorber to each other so that there is a distance (h₁)therebetween, whereupon the cover glass, the absorber, and the foresealing form the fore space, filling up the fore space with a first lowthermal conductive gas (136), attaching, by the back sealing (170), theinsulation part and the absorber to each other so that there is adistance (h₂) therebetween, whereupon the insulation part, the absorber,and the back sealing form the back space, and filling up the back spacewith a second low thermal conductive gas (176).